i) Field of Invention
This application generally relates to radar, and more particularly, to non-linear radar and processing steps, which exploit non-linear target responses.
ii) Description of Related Art
Historically, radar systems have operated on signals that are assumed to be echoes produced by linear systems. In linear radar systems, a pulse transmitted at one frequency will reflect off an object and produce a receive signal at the same frequency. This paradigm generally functions well, enabling radar systems to detect targets provided that their signatures are sufficiently different from those of natural clutter objects. Unfortunately, it has been demonstrated that certain clutter objects produce large linear responses to radar probe signals. For example, trees and rocks are capable reflecting relatively large amounts of energy, making it difficult for radar operators to distinguish them from targets of interest.
Advances in radar technology have made the problem somewhat more tractable. Modern synthetic aperture radar (SAR) systems are capable of achieving high resolution in both downrange and cross-range. While these systems produce detailed imagery of a scene, the detection of smaller targets can still be problematic. For example, targets that are only a few inches in diameter may produce a radar signature that is indistinguishable from the clutter background. Modern systems that exploit Doppler phenomena face a similar problem. In this case, large returns from stationary clutter objects can obscure slow-moving targets and, especially, if the targets reflect only a small amount of energy relative to the nearby clutter. It is the width of the main clutter lobe that helps fix the minimum detectable velocity achieved by a moving target indication (MTI) system.
Improvements in non-linear radar would be useful.